A TDD (time division duplex) frame structure in a long term evolution (LTE) system is as shown in FIG. 1. In such a frame structure, a 10 ms radio frame is divided into two half-frames; each half-frame is divided into 10 time slots equally of a length of 0.5 ms; every two time slots constitute a subframe of a length of 1 ms; a radio frame contains 10 subframes (numbered from 0 to 9); and a radio frame contains 20 time slots (numbered from 0 to 19). For a normal cyclic prefix (CP) of a length of 5.21 μs or 4.69 μs, a time slot contains 7 uplink/downlink symbols equally of a length of 66.7 μs (7×66.7 μs), wherein the length of the CP of the first symbol is 5.21 μs, and that of each of the remaining 6 symbols is 4.69 μs. For an extended CP of a length of 16.67 μs, a time slot contains 6 uplink/downlink symbols. Additionally, in such a frame structure, the configuration characteristics of the subframe are as follows:
(1) subframe 0 and subframe 5 are always reserved for downlink transmission;
(2) the downlink-to-uplink switch-point with a periodicity of 5 ms or 10 ms is supported;
(3) subframe 1 and subframe 6 are special subframes, which are used for transmitting 3 special time slots that are a downlink pilot time slot (DwPTS), a guard period (GP) and an uplink pilot time slot (UpPTS), wherein
the DwPTS is used for downlink transmission;
the GP refers to protection time, in which no data is transmitted; and
the UpPTS is used for uplink transmission, and contains at least 2 uplink SC-FDMA symbols for transmitting physical random access channels (PRACHs);
(4) in case of the downlink-to-uplink switch-point with a periodicity of 5 ms, subframe 2 and subframe 7 are always reserved for uplink transmission;
(5) in case of the downlink-to-uplink switch-point with a periodicity of 10 ms, the DwPTS is present in two half-frames, the GP and the UpPTS are present in the first half-frame, the time length of the DwPTS in the second half-frame is 1 ms, subframe 2 is used for uplink transmission, and subframe 7-9 are used for downlink transmission;
(6) primary-synchronization channel (P-SCH) signals are sent in the first Orthogonal Frequency Division Multiplexing (OFDM) symbol included in the DwPTS; and secondary-synchronization channel (S-SCH) signals are sent in the last OFDM symbols included in the time slot 1 and the time slot 11, and the bandwidth of a frequency-domain is 1.08 MHz; and
(7) at present, it is prescribed that at least 3 OFDM symbols are included in the DwPTS.
Physical hybrid ARQ indicator channel (PHICH) signals are sent in the first n OFDM symbols included in every common subframe used for downlink transmission, wherein n is 1 or 3 in unicast channels and is 1 or 2 in multicast channels.
If the PHICH signals are still sent in the DwPTS by the sending method for the common subframe and the primary-synchronization signals remain being sent in the first OFDM symbol included in the DwPTS, a confliction may occur between the physical time-frequency position to which the PHICH signals are mapped and the physical time-frequency position to which the primary-synchronization signals are mapped. Therefore, it is required to propose a technical solution for solving the problem of the confliction between the P-SCH signals and the PHICH signals in the DwPTS.